mailcow-dockerized-docs/docs/u_e-postfix-anonym_headers.md

To disguise your users details like IP, email client, etc. we have to create a new file in data/conf/postfix/mailcow_anonymize_headers.pcre and insert the following:

/^\s*Received:.*Authenticated sender:(.+)/
    REPLACE Received: from localhost (localhost [127.0.0.1]) (Authenticated sender:$1
/^\s*User-Agent/        IGNORE
/^\s*X-Enigmail/        IGNORE
/^\s*X-Mailer/          IGNORE
/^\s*X-Originating-IP/  IGNORE
/^\s*X-Forward/         IGNORE

Next we need to add the following to data/conf/postfix/main.cf:

smtp_header_checks = pcre:/opt/postfix/conf/mailcow_anonymize_headers.pcre

Then restart Postfix:

docker exec -it $(docker ps -qf name=postfix-mailcow) postfix reload